1. Field of the Invention
This invention relates to a contact device and more specifically to a contact device to be attached to an electromagnetic switch for increasing the number of contacts.
2. Description of the Related Art
An electromagnetic contactor, such as an auxiliary relay, usually has auxiliary contacts. Occasionally, more auxiliary contacts are needed due to construction of a controlled circuit. In such a case, a separate contact device is attached to an electromagnetic contactor or an auxiliary relay to increase the number of the auxiliary contacts.
FIG. 3 is a side-elevational view showing a conventional contact device 1 attached to a head portion of a conventional electromagnetic contactor 2. FIG. 4 is a perspective view of the contact device 1 of FIG. 3. FIG. 5 is a perspective view of the electromagnetic contactor 2 of FIG. 3. When the two are to be connected together, frame hook portions 12 formed on a frame 11 of the contact device 1 are inserted in an engaging portion 21 of the electromagnetic contactor 2 to effect the desired connection. At this time, a contact support connector portion 13a of the contact device 1 is connected to a contact support 22 of the electromagnetic contactor 2. Through the operation of the contact support 22 of the electromagnetic contactor 2, a contact support 13 of the contact device 1 is driven (upward and downward in the drawings) to thereby open and close a contact (not shown). A conventional a-contact is shown in FIG. 6. In FIG. 6, fixed a-contacts 14a are mounted within a frame 11. A conventional b-contact is shown in FIG. 7. In FIG. 7, fixed b-contacts 14b are mounted within the frame 11. The movable contact 15a (FIG. 6), 15b (FIG. 7) is supported on the contact support 13 through a contact spring 16. In the a-contact construction, the movable contact 15a is provided in corresponding relation to the fixed contact 14a, and in the b-contact construction, the movable contact 15b is provided in corresponding relation to the fixed contact 14b.
In such conventional contact devices, considering the disengagement of the contact support 13 from the frame 11 when all the contacts are of a b-contact construction as shown in FIG. 7, the movable contact 15b is engageable with a distal end 14b.sub.1 of the U-shaped fixed b-contact 14b, which thus serves as a stopper for preventing the contact support 13 from becoming disengaged from the frame 11.
FIG. 8 is a cross-sectional view of a second embodiment of a conventional b-contact construction which differs from that of FIG. 7 in that each fixed b-contact 14b' is of a flat plate-like shape, and that a cover 17 is provided to serve as a stopper for preventing the contact support 13 from being disengaged from the frame 11.
As discussed above, conventional contact devices are shown in FIGS. 6-8. The conventional contact device of a b-contact construction needs a stopper so that a contact support can not be disengaged from a frame. In FIG. 7, a fixed contact has a U-shaped cross-section, and a problem arises from this that since the width H of this U-shape is large, its dimension in a direction of movement of the contact support is large. With respect to the example shown in FIG. 8, since the cover is provided as a stopper, the number of the component parts as well as the time required for assembly is increased, resulting in increased costs.
It is an object of the present invention to provide a contact device which does not increase the dimension of a stopper, provided for preventing the disengagement of a contact support, in a direction of movement of the contact support, and also does not cause increased costs.